/Engine/Plugins/Online/OnlineSubsystemUtils/Source/OnlineSubsystemUtils/Public/OnlineSubsystemUtils.h
Gets anFNamethat uniquely identifies an instance of OSS
anFNameof format Subsystem:Context_Id in PlayInEditor or Subsystem everywhere else
[FName](API\Runtime\Core\UObject\FName) GetOnlineIdentifier ( const [FWorldContext](API\Runtime\Engine\Engine\FWorldContext) & WorldContext, const [FName](API\Runtime\Core\UObject\FName) Subsystem ) const